Bruce Hammock

The article, “Triclosan Promotes Liver Tumor Development,” highlights the team's discovery that triclosan, an antimicrobial commonly found in soaps, shampoos, toothpastes and many other household products, causes liver fibrosis and cancer in laboratory mice through molecular mechanisms that are also relevant in humans. 

Robert Tukey, a UC San Diego professor in the departments of Chemistry and Biochemistry and Pharmacology, led the study with Hammock, who has a joint appointment in the Department of Entomology and Nematology, and Comprehensive Cancer Center at UC Davis. Tukey and Hammock are directors of National Institute of Environmental Health Sciences Superfund Programs at their respective campuses.

Robert Tukey

The team, including San Diego-based scientist Mei-Fei Yueh, investigated long-term exposure to triclosan in mice by treating them with triclosan for 6 months, which is roughly equivalent to 18 human years. They then compared the livers of exposed mice with those of mice not exposed to triclosan. Researchers found that chronic exposure to triclosan in mice caused liver damage and liver cell death. They also discovered that triclosan exposure in mice increased susceptibility to tumor formation through enhanced cell growth, liver fibrosis (excessive accumulation of proteins in the liver), and proinflammatory responses, which are circumstances within which human cancer forms.

The scientists found that triclosan interferes with a nuclear receptor, known as the constitutive androstane receptor, that plays a role in detoxifying the blood. To compensate for this interference, the liver overproduces cells, which can lead to fibrosis and cancer.

PNAS co-authors included Koji Taniguchi, Shujuan Chen and Michael Karin, UC San Diego; and Ronald M. Evans, Salk Institute for Biological Studies.

Related Links
The Dirty Side of Soap
PNAS Paper, "The Commonly Used Antimicrobial Additive Triclosan Is a Liver Tumor Promoter"